Optical plate with micro-structures and backlight module using same

ABSTRACT

An exemplary optical plate includes a base and an array of micro-structures. The base includes a first surface and a second surface opposite to the first surface. The micro-structures are provided at the first surface. Each micro-structure includes a base surface substantially coplanar with the first surface of the base and two side surfaces. The base surface has an approximately olive-shaped profile enclosed by two arc-outlines. The two side surfaces extend obliquely from the two arc-outlines and intersect at a ridge of the micro-structure.

BACKGROUND OF THE DISCLOSURE

1. Field of the Disclosure

The present invention relates to optical plates and backlight modulesusing optical plates.

2. Description of Related Art

A typical liquid crystal display (LCD) device includes an LCD panel, anda backlight module mounted behind the LCD panel for supplying lightbeams thereto. The backlight module mainly includes a light source and aplurality of optical elements arranged in an order to provide uniformillumination to the LCD panel.

Referring to FIG. 9, a typical backlight module 100 includes a frame 11,a plurality of illuminators 12, a first diffuser plate 13, an opticalplate 10 and a second diffuser plate 14, arranged in that order frombottom to top. Referring also to FIG. 10, the optical plate 10 includesa main body 101 and a prism layer 103 formed on the main body 101. Aplurality of V-shaped prisms 105 are formed at an outside surface of theprism layer 103. The first and the second diffuser plates 13, 14 arerespectively used to scatter light beams transmitting therethrough. Theoptical plate 10 is used to control light beams transmittingtherethrough to emit from the optical plate 10 along predetermineddirections generally perpendicular to a liquid crystal panel (not shown)located above the backlight module 100, and used to converge the lightbeams toward a central region of the backlight module 100 fortransmission to the liquid crystal panel.

However, the diffuser plates 13, 14 and the optical plate 10 absorb aportion of the light beams transmitting therethrough. In addition, anair gap typically exists at the interface between each of the diffuserplates 13, 14 and the optical plate 10, and the gapped interface resultsin some back reflection of light transmitting therethrough. For thesereasons, the backlight module 100 typically has reduced lighttransmission and reduced brightness of light provided to the liquidcrystal panel. That is, the utilization of light beams and theefficiency of the backlight module are limited.

What is needed, therefore, is a backlight module which can overcome thedescribed limitations.

SUMMARY

An optical plate includes a base and a plurality of micro-structures.The base includes a first surface and a second surface opposite to thefirst surface. The micro-structures are provided at the first surface.Each micro-structure includes a base surface substantially coplanar withthe first surface of the base and two side surfaces. The base surfacehas an approximately olive-shaped profile enclosed by two arc-outlines.The two side surfaces extend obliquely from the two arc-outlines andintersect at a ridge of the micro-structure.

Other novel features and advantages will become more apparent from thefollowing detailed description when taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The components in the drawings are not necessarily drawn to scale, theemphasis instead placed upon clearly illustrating the principles of atleast one embodiment. In the drawings, like reference numerals designatecorresponding parts throughout the various views, and all the views areschematic.

FIG. 1 is a three-dimensional view of an optical plate according to anexemplary embodiment of the present disclosure.

FIG. 2 is essentially an enlarged, three-dimensional view of amicro-structure in the form of a protrusion provided on a first surfaceof the optical plate of FIG. 1.

FIG. 3 is a view of a projection on a Y-Z plane formed by the protrusionof FIG. 2.

FIG. 4 is a view of a projection on an X-Z plane formed by theprotrusion of FIG. 2.

FIG. 5 is a view of a projection on an X-Y plane formed by theprotrusion of FIG. 1.

FIG. 6 is a side, cross-sectional view of a backlight module using theoptical plate of FIG. 1.

FIG. 7 is similar to FIG. 6, but showing a backlight module using anoptical plate according to an alternative embodiment of the presentdisclosure.

FIG. 8 is similar to FIG. 3, but showing a view in the case of aprotrusion according to an alternative embodiment of the optical plateof the present disclosure.

FIG. 9 is a side, cross-sectional view of a conventional backlightmodule.

FIG. 10 is an enlarged, three-dimensional view of an optical plate ofthe backlight module of FIG. 9.

DESCRIPTION OF EMBODIMENTS

Reference will now be made to the drawings to describe preferred andexemplary embodiments in detail.

Referring to FIG. 1, a three-dimensional view of an optical plateaccording to an exemplary embodiment of the present disclosure is shown.The optical plate 20 includes a base (not labeled) and a plurality ofmicro-structures 2011. The base includes a first surface 201 and asecond surface 203 at opposite sides thereof. The first surface 201 hasthe micro-structures 2011 formed thereat. In the illustrated embodiment,the micro-structures 2011 are arranged in a regular m×n array (matrix).

Each of the micro-structures 2011 is in the form of a protrusion.Referring also to FIG. 2, each of the micro-structures 2011 includes abottom surface 2012 and two side surfaces 2013. The bottom surface 2012has an approximately olive-shaped profile, and is enclosed by twoarc-outlines 2015 on the first surface 201. The two side surfaces 2013extend upward from the two arc-outlines 2015 and intersect along the topof the micro-structure 2011, thereby forming a ridge 2014. Referringalso to FIG. 5, the bottom surface 2012 includes a long axis 2016 and ashort axis 2017. A three-dimensional (3-D) Cartesian coordinate systemis defined, with the long axis 2016 coinciding with the X axis, theshort axis 2017 coinciding with the Y axis, and the intersection of theX axis and the Y axis coinciding with the origin. The direction of the Zaxis is the direction of extension of the micro-structure 2011perpendicularly up from the bottom surface 2012. The micro-structure2011 is symmetrical about the X-Z plane and symmetrical about the Y-Zplane. A path defining the shape of the bottom surface 2012 of themicro-structure 2011 satisfies the following equation:

$y = {S \times {\begin{Bmatrix}{y_{0} + {A \times \frac{1}{1 + {\exp\left( \frac{- \left( {x - x_{c} + \frac{w_{1}}{2}} \right)}{w_{2}} \right)}} \times}} \\\left( {1 - \frac{1}{1 + {\exp\left( \frac{- \left( {x - x_{c} + \frac{w_{1}}{2}} \right)}{w_{3}} \right)}}} \right)\end{Bmatrix}.}}$

In the above equation, x and y are Cartesian coordinates of any pointalong the path, A, y₀, x_(c), w₁, w₂, w₃ and S are constants, andpreferably, A, y₀, x_(c), w₁, w₂, w₃ and S satisfy the following ranges:−13.549<y₀<−9.549, −213.5<x<213.5, −1.0<x_(c)<1.0, 62.754<A<72.754,45.72<w₁<280.2, 8.01<w₂<53.03, 8.01<w₃<53.03, and 0.1<S<3.

The micro-structure 2011 is axially symmetrical about the X-Z plane,with the ridge 2014 located in the X-Z plane. When the micro-structure2011 is cut away by any vertical plane, a triangular section is created.Referring also to FIG. 3, when the micro-structure 2011 is cut away byany plane parallel to the Y-Z plane, a triangular section is created,with the triangular section having an apex angle θ and the trianglebeing an isosceles triangle. Any point along the ridge 2014 is definedby a coordinate z on the Z axis and a coordinate x on the X axis.Referring also to FIG. 4, the series of points follow a mathematicalrelationship to define a path of the ridge 2014. In particular, the pathdefining the shape of the ridge 2014 satisfies the following equation:

$z = {{y \times {\tan \left( {{90{^\circ}} - \frac{\theta}{2}} \right)}} = {S \times \begin{Bmatrix}{y_{0} + {A \times \frac{1}{1 + {\exp\left( \frac{- \left( {x - x_{c} + \frac{w_{1}}{2}} \right)}{w_{2}} \right)}} \times}} \\\left( {1 - \frac{1}{1 + {\exp\left( \frac{- \left( {x - x_{c} + \frac{w_{1}}{2}} \right)}{w_{3}} \right)}}} \right)\end{Bmatrix} \times {{\tan \left( {{90{^\circ}} - \frac{\theta}{2}} \right)}.}}}$

In the above equation, x and z are Cartesian coordinates of any pointalong the path of the ridge, A, y₀, x_(c), w₁, w₂, w₃ and S areconstants, and preferably, A, y₀, x_(c), w₁, w₂, w₃ and S, satisfy thefollowing ranges: −13.549<y₀<−9.549, −213.5<x<213.5, −1.0<x_(c)<1.0,62.754<A<72.754, 45.72<w₁<280.2, 8.01<w₂<53.03, 8.01<w₃<53.03,45°<θ<175°, and 0.1<S<3.

With the shape in the X-Y plane of the bottom surface 2012 of eachmicro-structure 2011 satisfying the first above-mentioned equation andthe shape in the X-Z plane of the ridge 2014 of the micro-structure 2011satisfying the second above-mentioned equation, the micro-structures2011 at the first surface 201 tend to concentrate the emitting angles ofthe output light beams. Therefore, the brightness provided by theoptical plate 20 can be increased.

The optical plate 20 is typically made of light-transmissible plastic.The plastic is selected from a group consisting of polymethylmethacrylate (PMMA), polycarbonate, polystyrene (PS), polyethyleneterephthalate (PET), styrene-methyl methacrylate copolymer, and anycombination thereof.

The micro-structures 2011 can be bonded on the first surface 201 of thebase after the base is already molded. Alternatively, themicro-structures 2011 can be integrally formed with the base in a samemolding step. In the latter case, a mold for forming the base has aplurality of grooves defined in a surface thereof. The grooves of themold correspond to the micro-structures 2011.

When the optical plate 20 is in use, a light source is provided adjacentthe second surface 203. The second surface 203 acts as an incidentsurface, and the first surface 201 acts as an emitting surface. Lightbeams emitted by the light source enter the optical plate 20 via thesecond surface 203, propagate within the optical plate 20, arereflected, refracted and diffracted at the micro-structures 2011, andexit from the first surface 201. The micro-structures 2011 are used toincrease the brightness of the output light beams.

The micro-structures 2011 are not limited to the above-describedembodiments. For example, in the above-described embodiments, two sidesof the ridge 2014 meeting at an apex of the ridge 2014 are symmetricallyopposite each other, and are each inclined relative to the X axis at thesame angle. In alternative embodiments, the inclined angles of the twosides of the ridge 2014 can be different from each other. That is, thetwo sides of the ridge 2014 in the X-Z plane are asymmetric. Inaddition, the micro-structures 2011 may be arranged in an array ofparallel lines of micro-structures 2011, with the micro-structures 2011in each line being staggered relative to the micro-structures 2011 ineach of the two adjacent lines. Furthermore, the micro-structures 2011are not limited to protrusions. Instead, referring to FIG. 7, themicro-structures 2011 may be a plurality of portions of the opticalplate 20 having grooves defined therein. The shape of each groove is thesame as the shape of each micro-structure 2011. However, each groove isoriented upside-down compared to the orientation of the micro-structure2011. The grooves may be arranged in a regular m×n array, or may bearranged in a staggered fashion similar to that described above.Alternatively, the optical plate 20 can have a combination of themicro-structures 2011 and the grooves. In such case, themicro-structures 2011 and the grooves may be arranged alternately withrespect to each other.

Referring to FIG. 6, a backlight module 200 using the optical plate 20is shown. The backlight module 200 includes a frame 21, a light source22, and the optical plate 20 arranged generally in that order frombottom to top.

The frame 21 is made of metallic or plastic material, and may have ahigh reflection index. Further or alternatively, an inner surface of theframe 21 may be coated with a reflective material.

The light source 22 may be a plurality of cold cathode fluorescent lamps(CCFLs), or may be a plurality of light emitting diodes (LEDs). Lightbeams emitted by the light source 21 enter the optical plate 20 via thesecond surface 203, propagate within the optical plate 20, arereflected, refracted and diffracted at the micro-structures 2011, andexit from the first surface 201 of the optical plate 20. Due to theeffect of the micro-structures 2011, the light emitted from the firstsurface 201 is concentrated within a predetermined viewing angle. Theconvergence function of the optical plate 20 further enhances thebrightness of the backlight module 200.

In order to verify the effectiveness of the optical plate 20, ninetesting points were designated for the above-described backlight module100 (i.e., without the micro-structures 2011), and for the backlight 200(with the micro-structures 2011). Thus a contrast test of the brightnessof the backlight module 200 was carried out. The test results are shownin the following table:

Brightness of Brightness of Number of backlight module backlight moduleEnhancement of testing point 100 (cd/m²) 200 (cd/m²) brightness 11775.00 2027.20 14.2% 2 1652.60 1904.20 15.2% 3 1592.80 1926.80 20.9% 41771.20 2054.60 16.0% 5 1623.80 1919.00 18.2% 6 1497.80 2082.00 39.0% 71624.20 2220.40 36.7% 8 1570.00 2009.60 28.0% 9 1566.20 2198.20 40.3%

From the table above, it can be concluded that the brightness of thebacklight module 200 with the micro-structures 2011 on the emittingsurface of the optical plate 20 is higher than that of the backlightmodule 100. Moreover, the effect of the micro-structures 2011 issignificant, with the brightness being increased at least 14 percent.

In other embodiments, a diffuser plate can be positioned between thelight source 22 and the optical plate 20, to further increase thebrightness of the backlight module 200.

Various modifications and alterations are possible within the ambit ofthe disclosure herein. For example, referring to FIG. 8, the ridge alongthe top of the micro-structure 2011 can be milled or otherwise formedsuch that the ridge has a curved cross-section rather than an angularcross-section. With any of the above-described configurations, thecorresponding backlight module may provide substantially uniformintensity of output light beams. That is, an overall intensitydistribution of the output light beams is relatively even.

It is believed that the present embodiments and their advantages will beunderstood from the foregoing description, and it will be apparent thatvarious changes may be made thereto without departing from the spiritand scope of the invention or sacrificing all of its materialadvantages, the examples hereinbefore described merely being preferredor exemplary embodiments of the invention.

1. An optical plate, comprising: a base comprising a first surface and asecond surface at opposite sides thereof; and a plurality ofmicro-structures provided at the first surface; wherein eachmicro-structure defines a base surface substantially coplanar with thefirst surface of the base, and two side surfaces, the base surface hasan approximately olive-shaped profile enclosed by two arc-outlines, andthe two side surfaces extend obliquely from the two arc-outlines andintersect at a ridge of the micro-structure.
 2. The optical plate ofclaim 1, wherein the two side surfaces intersect at a top of themicro-structure, forming the ridge.
 3. The optical plate of claim 2,wherein the base surface defines a long axis and a short axis, athree-dimensional (3-D) Cartesian coordinate system is defined with thelong axis coinciding with the X axis, the short axis coinciding with theY axis, the intersection of the X axis and the Y axis coinciding withthe origin, and the direction of the Z axis being the direction of theextension of the micro-structure perpendicularly up from the basesurface, and a path defining the shape of the base surface satisfies thefollowing equation: $y = {S \times \begin{Bmatrix}{y_{0} + {A \times \frac{1}{1 + {\exp\left( \frac{- \left( {x - x_{c} + \frac{w_{1}}{2}} \right)}{w_{2}} \right)}} \times}} \\\left( {1 - \frac{1}{1 + {\exp\left( \frac{- \left( {x - x_{c} + \frac{w_{1}}{2}} \right)}{w_{3}} \right)}}} \right)\end{Bmatrix}}$ wherein, x and y are Cartesian coordinates of any pointalong the path, A, y₀, x_(c), w₁, w₂, w₃ and S are constants, and A, y₀,x_(c), w₁, w₂, w₃ and S satisfy the following ranges: −13.549<y₀<−9.549,−213.5<x<213.5, −1.0<x_(c)<1.0, 62.754<A<72.754, 45.72<w₁<280.2,8.01<w₂<53.03, 8.01<w₃<53.03, and 0.1<S<3.
 4. The optical plate of claim3, wherein a path defining the shape of the ridge satisfies thefollowing equation:${z = {y \times {\tan \left( {{90{^\circ}} - \frac{\theta}{2}} \right)}}},{\left( {{45{^\circ}} < \theta < {175{^\circ}}} \right).}$5. The optical plate of claim 1, wherein the micro-structures compriseprotrusions extending upward from the first surface of the base.
 6. Theoptical plate of claim 1, wherein the micro-structures comprise groovesextending inward from the first surface of the base.
 7. The opticalplate of claim 4, wherein a triangular section is created when themicro-structure is cut away by any plane parallel to the Y-Z plane, andthe triangle is an isosceles triangle.
 8. The optical plate of claim 1,wherein a transverse cross-section of the ridge is angular.
 9. Theoptical plate of claim 1, wherein a transverse cross-section of theridge is curved.
 10. A backlight module, comprising: a light source; andan optical plate comprising a base and a plurality of micro-structures,the base comprising a first surface and a second surface at oppositesides thereof, the micro-structures provided at the first surface, andthe second surface facing toward the light source; wherein eachmicro-structure defines a base surface substantially coplanar with thefirst surface of the base, and two side surfaces, the base surface hasan approximately olive-shaped profile enclosed by two arc-outlines, andthe two side surfaces extend obliquely from the two arc-outlines andintersect at a ridge of the micro-structure.
 11. The backlight module ofclaim 10, wherein the two side surfaces intersect at a top of themicro-structure, forming the ridge.
 12. The backlight module of claim11, wherein the base surface defines a long axis and a short axis, athree-dimensional (3-D) Cartesian coordinate system is defined with thelong axis coinciding with the X axis, the short axis coinciding with theY axis, the intersection of the X axis and the Y axis coinciding withthe origin, and the direction of the Z axis being the direction of theextension of the micro-structure perpendicularly up from the basesurface, and a path defining the shape of the base surface satisfies thefollowing equation: $y = {S \times \begin{Bmatrix}{y_{0} + {A \times \frac{1}{1 + {\exp\left( \frac{- \left( {x - x_{c} + \frac{w_{1}}{2}} \right)}{w_{2}} \right)}} \times}} \\\left( {1 - \frac{1}{1 + {\exp\left( \frac{- \left( {x - x_{c} + \frac{w_{1}}{2}} \right)}{w_{3}} \right)}}} \right)\end{Bmatrix}}$ wherein, x and y are Cartesian coordinates of any pointalong the path, A, y₀, x_(c), w₁, w₂, w₃ and S are constants, and A, y₀,x_(c), w₁, w₂, w₃ and S satisfy the following ranges: −13.549<y₀<−9.549,−213.5<x<213.5, −1.0<x_(c)<1.0, 62.754<A<72.754, 45.72<w₁<280.2,8.01<w₂<53.03, 8.01<w₃<53.03, and 0.1<S<3.
 13. The backlight module ofclaim 12, wherein a path defining the shape of the ridge satisfies thefollowing equation:${z = {y \times {\tan \left( {{90{^\circ}} - \frac{\theta}{2}} \right)}}},{\left( {{45{^\circ}} < \theta < {175{^\circ}}} \right).}$14. The backlight module of claim 10, wherein the micro-structurescomprise protrusions extending upward from the first surface of thebase.
 15. The backlight module of claim 10, wherein the micro-structurescomprise grooves extending inward from the first surface of the base.16. The backlight module of claim 13, wherein a triangular section iscreated when the micro-structure is cut away by any plane parallel tothe Y-Z plane, and the triangle is an isosceles triangle.
 17. Thebacklight module of claim 10, wherein a transverse cross-section of theridge is angular.
 18. The backlight module of claim 10, wherein atransverse cross-section of the ridge is curved.
 19. An optical plate,comprising: a base comprising a first surface and a second surface atopposite sides thereof; and a plurality of micro-structures provided atthe first surface; wherein in a three-dimensional (3-D) Cartesiancoordinate system, each micro-structure is defined by a series ofparallel isosceles triangles each defined in a plane parallel to a Y-Zplane and symmetrical about an X-Z plane with the series of trianglesaligned along an X axis, two vertexes of each triangle located in theX-Y plane, another vertex of each triangle located in the X-Z plane, thevertexes of the series of triangles in the X-Y plane forming anapproximately olive-shaped profile, and the vertexes of the series oftriangles in the X-Z plane forming a ridge profile.
 20. The opticalplate of claim 19, wherein a path defining the shape of the vertexes ofthe series of triangles in the X-Y plane satisfies the followingequation: $y = {S \times \begin{Bmatrix}{y_{0} + {A \times \frac{1}{1 + {\exp\left( \frac{- \left( {x - x_{c} + \frac{w_{1}}{2}} \right)}{w_{2}} \right)}} \times}} \\\left( {1 - \frac{1}{1 + {\exp\left( \frac{- \left( {x - x_{c} + \frac{w_{1}}{2}} \right)}{w_{3}} \right)}}} \right)\end{Bmatrix}}$ wherein, x and y are Cartesian coordinates of any pointalong the path, A, y₀, x_(c), w₁, w₂, w₃ and S are constant, and A, y₀,x_(c), w₁, w₂, w₃ and S, satisfy the following ranges:−13.549<y₀<−9.549, −213.5<x<213.5, −1.0<x_(c)<1.0, 62.754<A<72.754,45.72<w₁<280.2, 8.01<w₂<53.03, 8.01<w₃<53.03, and 0.1<S<3.